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Katabuchi M.,Tohoku University | Kurokawa H.,Tohoku University | Davies S.J.,Harvard University | Tan S.,Sarawak Forestry Corporation | Nakashizuka T.,Tohoku University
Journal of Ecology | Year: 2012

Habitat filtering and limiting similarity have been proposed as two opposing forces structuring community memberships. Community assembly theory proposes habitat filtering as a mechanism restricting community membership according to the ecological strategies of species in a given environment. Limiting similarity posits that some species exclude others that are ecologically similar. We quantified nine ecophysiological and life-history traits for 80 dipterocarp species in the 52-ha Lambir Forest Dynamics Plot (FDP; Lambir Hills National Park, Sarawak, Malaysia). We studied forests on four soil types differing in fertility and moisture, focusing on soil resource availabilities as environmental determinants of habitat filtering processes. We used a null-model approach to detect the strengths of habitat filtering and limiting similarity. We quantified the relative contributions of soil resources (nutrients and water) to habitat filtering by comparing the strength of habitat filtering processes (i.e. effect sizes) at the overall plot scale and at the individual soil-type scale. We also compared the strengths of assembly processes among soil types. Compared to a null model at microscale (20×20m), trait range and variance were reduced for seven of nine functional traits, suggesting the importance of habitat filtering in the dipterocarp community. We also found a broader distribution of five traits, and more even spacing for seven traits (20×20m), which is consistent with the concept of limiting similarity. Randomizations that swapped species occurrences within soil types (i.e. null models removing soil effects in assembly processes) were much closer to observed values, and there were no phylogenetic constraints on habitat association. Hence, soil resource availability acted as a habitat filtering mechanism in the FDP; relative contributions to habitat filtering ranged from 35% for seed mass to 77% for relative growth rate. Furthermore, soil types apparently affected the strengths of habitat filtering and limiting similarity. Synthesis.We demonstrate that soil resource availability is a crucial determinant of habitat filtering in this species-rich tropical rain forest; the strengths of assembly processes differed among soil types. Variation in soil resource availability can shape the distribution of traits through community assembly processes, promoting trait diversification and species coexistence. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society.


Russo S.E.,University of Nebraska - Lincoln | Russo S.E.,Harvard University | Cannon W.L.,University of Nebraska - Lincoln | Elowsky C.,University of Nebraska - Lincoln | And 3 more authors.
American Journal of Botany | Year: 2010

Premise of the study: Quantifying variation in functional traits associated with shifts in the species composition of plant communities along resource gradients helps identify environmental attributes important for community assembly. Stomates regulate the balance between carbon assimilation and water status in plants. If environmental attributes affecting photosynthetic water-use efficiency govern species distribution along an edaphic gradient, then adaptive variation in stomatal traits of plant species specializing on different soils should reflect belowground resource availability. Methods: We tested this hypothesis by quantifying stomatal trait variation in understory saplings of 28 Bornean tree species in relation to gas exchange and water-use efficiency (WUE). Key results: Comparisons between congeneric specialists of the more fertile, moister clay and the less fertile, well-drained sandy loam revealed little evidence of similar shifts in stomatal traits across genera, nor was stomatal pore index correlated with gmax, Amax, or WUE (Amax/gmax or Δ13 C), suggesting that stomates may be overbuilt in these shaded juveniles. Amax was higher on sandy loam, likely due to higher understory irradiance there, but there were no other significant differences in gas exchange or WUE. Conclusions: Despite substantial diversity in stomatal anatomy, there were few strong relationships between stomatal, photosynthetic, and WUE traits in relation to soil resources. Routine differences in water availability therefore may not exert a dominant control on the distributions of these Bornean tree species. Furthermore, the clades represented by these 12 genera may possess alternative functional designs enabling photosynthetic WUE that is sufficient to these humid, understory environments, due to whole plant-functional integration of stomatal traits with other, unmeasured traits influencing gas exchange. © 2010 Botanical Society of America.


Sang J.,Sarawak Forestry Corporation | Kiew R.,Malaysian Forest Research Institute
Phytotaxa | Year: 2016

Nine Begonia species are recorded from the Batang Ai National Park and the forest area adjacent to the Park. Of these, six species are described here as new (Begonia acidulenta, Begonia bayae, Begonia compacta, Begonia edgariana, Begonia jenginensis and Begonia tebiang). All species belong to section Petermannia. A key to the new species and three species previously described by Lin et al. (2014) is provided. Following the guidelines for the IUCN Categories and Criteria, the proposed conservation status of the seven new species known from the national park is assessed as “Least Concern”. © 2016 Magnolia Press.


Jong L.K.,Sarawak Forestry Corporation | Sani H.B.,University Malaysia Sarawak
Journal of Tropical Forest Science | Year: 2012

Application of rooted cuttings derived from epicormic shoots from mature trees of Dryobalanops beccarii and D. rappa in current tree propagation and improvement programmes is suggested and discussed. Development of epicormic shoot indicated partial rejuvenation which was exhibited by plagiotropic growth habit, adult leaf morphology and delayed bud flushing of rooted cuttings. The juvenility of epicormic shoots showed that the 'ageing' component of cyclophysis had been reversed by the 'maturation' component which remained unaltered. The incomplete rejuvenation was further demonstrated by poor rooting of cuttings derived from epicormic shoots. The potential of using these characteristics as possible markers of juvenility and maturity is also discussed. Cuttings derived from epicormic shoots from the stump of D. beccarii and D. rappa rooted more readily than those from other parts of the tree bole. It was suggested that epicormic shoots obtained from stumps were more juvenile than those from upper part of the stem. This phenomenon, described as topophysis, supported the theory that maturation occurred in different phases. © Forest Research Institute Malaysia.


Peay K.G.,University of California at Berkeley | Kennedy P.G.,Lewis And Clark College | Davies S.J.,Harvard University | Tan S.,Sarawak Forestry Corporation | And 2 more authors.
New Phytologist | Year: 2010

Relatively little is known about diversity or structure of tropical ectomycorrhizal communities or their roles in tropical ecosystem dynamics. In this study, we present one of the largest molecular studies to date of an ectomycorrhizal community in lowland dipterocarp rainforest. We sampled roots from two 0.4 ha sites located across an ecotone within a 52 ha forest dynamics plot. Our plots contained > 500 tree species and > 40 species of ectomycorrhizal host plants. Fungi were identified by sequencing ribosomal RNA genes. The community was dominated by the Russulales (30 species), Boletales (17), Agaricales (18), Thelephorales (13) and Cantharellales (12). Total species richness appeared comparable to molecular studies of temperate forests. Community structure changed across the ecotone, although it was not possible to separate the role of environmental factors vs host plant preferences. Phylogenetic analyses were consistent with a model of community assembly where habitat associations are influenced by evolutionary conservatism of functional traits within ectomycorrhizal lineages. Because changes in the ectomycorrhizal fungal community parallel those of the tree community at this site, this study demonstrates the potential link between the distribution of tropical tree diversity and the distribution of tropical ectomycorrhizal diversity in relation to local-scale edaphic variation. © 2009 New Phytologist.

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